The present invention relates to hoses, particularly to car hoses, for example, car hoses for use as a positive crank case ventilation hose, a vacuum regulator valve hose, a cruise control vacuum hose and a brake vacuum hose, wherein the hose is manufactured by extrusion molding without vulcanizing.
For a conventional vacuum hose used for cars, generally, a two-layer structured hose is used in which epichlorohydrin rubber (ECO) superior in heat resistance and oil resistance, acrylonitrile-butadiene rubber (NBR) or the like is used in an inner layer, and chlorosulfonated polyethylene (CSM) superior in wear resistance is used in an outer layer. Since these rubber hoses are heavy, and a rubber kneading process and a vulcanizing process are necessary, a manufacture process is complicated and it is difficult to reduce costs. Moreover, since different materials forming the two-layer structure cannot be separated, they cannot be recycled or used.
In recent years, from requests for the saving of resources and the lightening of cars, instead of the rubber hoses, for example, resin hoses have been used in which nylon (PA)6, or nylon (PA)12 is used in sensing hoses, and the like. The conventional resin hose is molded by extruding one type of resin into one layer.
However, although the conventional resin hose is of one type of material, and can be recycled, its flexibility is insufficient, and the hose cannot directly be inserted or attached to an opponent component like the rubber hose. Moreover, not only the resin hose is inferior in inserting property as described above, but also the resin hose has to use a quick connector (O ring seal) or a seal agent to secure the sealing property equal to that of the rubber hose. Another problem is that the conventional resin hose is inferior to the rubber hose in flexibility and vibration absorption.
This invention has been developed in consideration of the above-described present situation, and an object thereof is to provide the following hose.
Specifically, an object of the present invention is to provide a hose which is superior in flexibility and vibration absorption, which can directly be inserted and attached to the opponent component, and which can secure a sealing property.
Moreover, an object of the present invention is to provide a hose which intends to be reduced in weight and cost.
Furthermore, an object of the present invention is to provide a recyclable hose.
According to the present invention, there is provided a hose which comprises an inner layer as an inside layer and an outer layer disposed on the outer peripheral surface of the inner layer. An olefin thermoplastic elastomer comprising polypropylene (PP) and acrylonitrile-butadiene rubber (NBR) is used in the inner layer, and an olefin thermoplastic elastomer comprising polypropylele (PP) and ethylene-propylene-diene rubber (EPDM) is used in the outer layer to perform molding.
By forming the inner and outer layers by the above-described materials, a hose superior in oil resistance, fuel oil resistance, and heat resistance can be obtained, and additionally by employing a low specific-weight material, lightening can be realized. Moreover, since the whole is of the same olefin thermoplastic elastomer, the vulcanizing process is unnecessary, and the manufacture can be performed only by extrusion molding. Therefore, since the reduction of the manufacture processes lowers the processing cost, the cost of the product can be reduced. Moreover, since the whole is formed of a thermoplastic resin, not by combining the thermoplastic resin and rubber as in the conventional art, the product is subjected to a thermal processing (post-processing) so that the configuration of the product can freely be changed (bend processing). Furthermore, since the whole is constituted of the thermoplastic material, it can be recycled, and reused as the resin material by melting or pelletizing the product.
Moreover, it is preferable to add an amine stabilizer, or a stabilizer formed of a mixture of thioether and hindered phenol to the olefin thermoplastic elastomer. The addition of the stabilizer can further enhance the heat resistance. The stabilizer is preferable in a range of 1 to 5 wt %. If it is 1 wt % or less, it does not act as the stabilizer, and if it is 5 wt % or more, kneading and mixing are difficult, and the stabilizer is possibly deposited on the surface. Moreover, the hardness of the olefin thermoplastic elastomer is preferably in a range of 60 to 90 in JIS A hardness. By setting the hardness to 60 to 90 in JIS A hardness, the hose inserting property, and hose extracting pressure can be enhanced.